


Unique

by Sarita1046



Category: Adventure Time
Genre: Canon compliant through Three Buckets, Coming In Pants, Coming Untouched, Confusion, Identity Issues, M/M, Mostly just using that tag as a potential trigger warning, selfcest but maybe not really?
Language: English
Status: Completed
Published: 2020-05-24
Updated: 2020-07-03
Packaged: 2021-03-03 08:21:29
Rating: Mature
Warnings: Creator Chose Not To Use Archive Warnings
Chapters: 2
Words: 3,466
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/24347905
Author URL: https://archiveofourown.org/users/Sarita1046/pseuds/Sarita1046
Summary: Fern sat up, glancing toward the golden horizon.“Ready for breakfast?” Finn asked, still quietly fascinated by Fern’s photosynthetic nature. “That’s crazy you can actually eat that way.”“It’s actually a pretty cool experience.”“Yeah? How?”“It’s like a rush…hard to explain. If you want, I can just show you?”
Relationships: Fern the Human/Finn the Human
Comments: 7
Kudos: 118





	1. Chapter 1

**Author's Note:**

> Musical inspiration: “Erev shel Shoshanim” (Evening of Roses) by David and the High Spirit
> 
> https://open.spotify.com/track/4PB1hLNm7RmNBiRzMjD72g?si=hp1HwfnCTXaCAsV0_7Rv1Q

Finn sighed, kicking away the furs that typically covered his bed. Beside him, Jake snored in the bureau drawer, a grating sound whose familiarity brought more comfort than ever.

Honestly, from the whirlwind experiences of meeting his birth mother – or what was left of her, anyway – to a catastrophic showdown with PB, Flame Princess and many others gone mad, including himself…the realization sort of just gobsmacked him in the face tonight. He hadn’t really taken the chance to digest it all. Hadn’t really _had_ the chance to register everything. 

Susan was out of their lives, bound for a whole other journey all her own. His mother didn’t seem keen on visiting Ooo just yet. And, well. Then, there was Fern. A wave of guilt tugged at his chest when he finally let himself acknowledge the fact that he had quite deliberately neglected to tell his grass double the main reason he’d wanted to seek out the Island in the first place – his, or he supposed _their_ mother.

Swiping his flesh hand over his forehead, he decided sleep wasn’t going to come just yet – not in this heat.

Pulling himself up the ladder leading to the lush treetop above their home, Finn halted a moment to let the crisp evening breeze soothe the sweat on his cheeks. Closing his eyes to enjoy the ensuing humid summer air, he drew a deep breath to peer up at the starry night sky. 

He couldn’t help but marvel at how, even from this distance, he could make out the various planets that decorated the vast black expanse. Martin, Orgalorg, Prismo, who knows what else, all represented something beyond even the immeasurable space he could see.

Shaking his head to avoid spacing out, Finn tore his eyes from the sky and finished his ascent up to the treetop.

As soon as he stood in the grass that covered the roof of his home, he drew his lower lip between his teeth. What had even driven him up here in the first place? Maybe the fresh air would do some good…

“Oh, hey.”

Fern’s voice to his right preceded Finn’s grass double emerging from the greenery beneath them, form murky in the pale starlight and absence of moon.

“Hey, Fern,” Finn replied, thankful he had avoided releasing one of those surprised shrieks at the unexpected greeting. “Catching some starlight?” 

“It’s sort of…relaxing,” Fern said after a thoughtful pause, as he stood. “Can’t sleep?”

“Just been thinkin’,” Finn answered truthfully, “My head’s gunked up from all this biz that’s been happening.”

“Yeah…” Fern trailed off for a stretch. “I guess I didn’t help by being useless when the elementals went nuts.”

“We’re not gonna do this again, are we?” Finn stretched out on the leafy ground, languid movements not matching the light frustration in his tone. “I literally turned into fire and went on a murderous rampage. You know we were _all_ useless.”

“Except LSP,” Fern’s voice seemed to smile in the dark, as he lay back beside Finn.

“Yeah, she was pretty helpful there at the end. Wasn’t expecting that,” Finn admitted. 

“Wasn’t expecting that whole reverse effect to happen or for LSP to be useful?”

Finn scoffed. “Come on, man, don’t be that way. LSP’s my friend, you know that.”

“All I really know is that she’s pretty much your only reference point for…things.”

At that, Finn focused again on the gentle breeze to quell the blush that rose to his cheeks. Darn shared memories. 

“I guess you would know that.”

“You and your misadventures with girls,” Fern chuckled in the darkness.

Finn fiddled with his shirt. “I mean…livin’ the way we do doesn’t exactly give enough time to overthink things. Jake and Lady are the only two I’ve ever seen work out.”

A stretch of silence overtook the treetop.

“It’s good, I guess…to at least be out of the sword. Moving around and all is a nice change of pace.”

Finn sighed, closing his eyes again. “Losing my arm was hard at first…then it just kept happening so I sorta got used to it. I can’t even imagine being trapped for so long…if I’m honest, I don’t blame you for giving it to that Grass Wizard. He screwed me over, too.”

“Yeah…but it’s been weird out here, too. Figuring out all your memories and what’s okay to say and not say.”

“You mean PB?” Finn guessed. “I’m guessing you haven’t seen Phoebe too much…”

“Right, PB,” Fern murmured, “she invited me to the castle once before all the elemental stuff.”

“What kind of assignment was it?”

Fern paused, and Finn wondered if he’d heard him.

“She…she asked if I’d be okay lying down and showing her how the shapeshifting deal works. I’m still figuring it out myself though, so…”

Finn’s relaxed state dissolved to a sensation that clenched his chest in a combination of surprise and…was it possessiveness? Maybe something similar to when he’d challenged PB on how she felt about him back in the day.

“Phoebe said she did that with her, too,” Finn replied, trying to diffuse his own feelings, “She says she likes to know what could possibly help her defenses...or pose a threat. Did you do it?”

“…yes.” That response took too long for Finn’s liking. “Being touched was…nice, because she wasn’t trying to kill me. And I put out those early feelings left over from you. She mostly looked me over a lot, not many tests.”

Finn stayed silent, toying with a bit of grass by his thigh. For some reason, the fact that Bonnie had waited until Finn left to ask this favor of Fern left a sour taste in Finn's mouth.

“Then Marcy came by with Peppermint Butler, and I think Bonnie had told him not to let her in. Marcy got mad, so Bonnie just told me to go.”

Finn’s chest relaxed a smidgen at the notion that his close friend had also found the situation strange. Slowly, he realized that maybe the possessiveness was more about Fern than about PB. If he'd needed one more piece of evidence to actually prove the princess's need for control, well...there it was. And it bothered him. He felt a responsibility to Fern…

“I met my mom,” the words tumbled out before he’d thought them through.

Despite a rustle beside him in the dark, Fern didn’t reply for a beat. “How was it?”

“You’re not mad?” Finn asked, turning toward Fern, once he’d realized his double had maneuvered to face him. “That I didn’t invite you along?”

“She’s your mom,” Fern said, eyes gazing past his almost languidly, “but you have no memories of her, so I technically have no connection.”

Finn recalled his mother referring to Fern as “the grass kid”. Fair point. “I guess I have no relation to the Grass Wizard either,” Finn said finally.

“Weird, huh,” Fern stated, “how we’re not actually the same guy at all. What I said before was wrong...calling myself human doesn't really make sense. It’s just the basic form the grass took from your memories. We're not really clones.” 

“Or even relatives,” Finn replied, “similar story with Jake though, but at least we grew up together.”

“Yeah, man, it’s crazy,” Fern said, shifting a bit where he lay, “though it is cool of you to treat me like family. It’s nice when things get tough.”

“As cool as Jake is,” Finn said, “I kinda like sleeping up here too. It’s a nice change from the bedroom.”

“I hope my company isn’t too much of a downer,” Fern said, and this time, Finn had to wonder if he was just fishing for compliments. 

He’d toss him a line.

“It’s some of the best company I’ve had sleeping outside.”

He could practically feel Fern smirk in the dark. “Better than LSP?”

“Ugh,” Finn threw his arm over his forehead, “you keep bringing that up.”

“Or Huntress Wizard?”

“I was never alone with her overnight,” Finn pointed out. “She was the one following me…at the stream. When you played the flute.”

“Living sword has its benefits.”

“I wonder what she’d think of you,” Finn mused, peering back at Fern.

“Too many nature beings,” Fern scoffed. “You’d think one would be enough.”

“You are enough,” Finn spoke yet again without realizing how it would sound, “…I mean, you gotta stop doubting yourself.”

“Thanks, man…the memories of you are odd too, you know. I remember being in that stream with you. I could feel the water.”

“We could go swimming sometime,” Finn said. “Today, if you want. Sun’s coming up.”

Fern sat up, glancing toward the golden horizon.

“Ready for breakfast?” Finn asked, still quietly fascinated by Fern’s photosynthetic nature. “That’s crazy you can actually eat that way.”

“It’s actually a pretty cool experience.”

“Yeah? How?”

“It’s like a rush…hard to explain. I can just show you, if you want?”

Squinting against the arriving dawn, Finn sat up and turned toward his double. “Is…that something I can feel, too?”

“Guess we can find out,” Fern replied, pulling down his own hat and slipping his fingers into Finn’s hand without moving his gaze from the horizon. The red and yellow flowers in those blond-green locks shone in the gold of the new morning.

Turning his own gaze back to the sunrise, Finn drew a deep breath. The inhale swiftly gave way to a sharp gasp, as a gentle, warm sensation flooded from his flesh hand that Fern held, up his own arm and spread throughout his chest at a rate that almost made his head spin.

Closing his eyes to steady his racing heart, he soon reveled in the soft heat that…hold up. Without opening his eyes to glance at Fern beside him, he took several long moments to make sure he was feeling it correctly. Yes, he was definitely stirring down there.

Glob, _why?_

For Grod knew what reason, his mind chose that moment to recall Fern both singlehandedly lifting Sweet P and holding down the Lich’s hand. His flesh tingled, a shiver coursing from his chest straight to his groin.

“Fern,” he spoke, opening his eyes and no longer worrying about appearance amidst the sudden panic. “Is this supposed to feel…”

“It’s cool,” the slightly scratchy brush of Fern’s thumb rubbed circles over the back of Finn’s hand, “I know what you mean.”

“So…when we were fishing that day before…before Sweet P came along, and you were eating…was it…”

“Naw,” Fern said, and Finn swallowed hard when his double scooted closer until their shoulders touched, joined hands resting on Finn’s knee. “I think it’s more intense when shared.”

“So I feel what you feel?” Finn asked before realizing Fern might not be able to tell what he was feeling. Hopefully not, as he could no longer ignore that pressure mounting between his legs.

“I’m technically feeding right now, but…yeah, there’s something extra for me, too. Combined energy, I guess. If it’s too much and you want a distraction from the buzz, I’m always up for another squoze.”

For some reason, the idle affection he’d felt at their closeness during sporadic past squozes emerged full force, forcing Finn to acknowledge what he had been avoiding – this wasn’t the first time he’d felt something like this intriguing pull towards Fern, and…well, it definitely wasn’t something he hated. 

Here goes nothing.

Pursing his lips, Finn drew Fern towards his chest. The mild scent of flowers filled his nose. As soon as Finn drew up his own knees and pulled Fern back against him, pleasure overran his senses and his crotch exploded in a surge of warmth.

Euphoria mixed with sheer horror, as he hoped the buffer of his knees would keep Fern from catching on despite the quiet yet heady moan that had just escaped him at the unexpected release. The only part of him that didn't hum with this strange and wonderful thrum was his mechanical arm that rested in the greenery beside them.

“It’s okay, man…” came Fern’s low tone, as he lay his head back against Finn’s shoulder, “I’m in the same boat.”

The human thought his mind might freeze over at the tremble that shook Fern, as his double rocked back against him, fingers maneuvering from their more superficial grip to lace through his own in a tight hold. Realizing he’d been panting, Finn quickly slowed his breathing. “Glob, I’m so sorry, I….”

“Unless you’re gonna say you want to keep this up, I don’t really want to hear it,” Fern murmured against his jaw.

“Everything’s normal,” Finn said aloud, mostly to calm himself as he glanced down to see Fern's other hand relaxing from the fist it'd been twisting in the grass beneath them, “we’re just two guys…”

“Enjoying the sunrise.”

The moment Jake called out from their bedroom, Finn’s trance shattered and the panic set in full force. “Well, it’s been fun for sure. I hope the…uh, food is good up here. I’m gonna go eat now, but I’ll see you later.”

Withdrawing his hand, Finn scrambled out of their embrace. Fern got to his feet before Finn could make it off the rooftop. “Finn, why are you freaking out?”

“I just…”

“It’s because you still think I’m you, right? Well, I told you, I’m not…it honestly almost feels like you want me to be. Another you? You think you’re just that amazing?”

Great, this was going so well…and his pajama pants were sticking to his inner thighs. The stark differences in their appearances suddenly all stood out, coaxing him even more to the person before him. The differently shaped face, the slightly more rigid movements…that lower-pitched voice. Similar base look to himself only with a power and fire that he could really start to crave...

He definitely seemed to have a type. Was he actually falling for a sword double? Why in the name of the globs did he always fall so _easily_? Bonnie, Phoebe...and he always managed to muck it up. His head swam.

“No, Fern! I told you, you _should_ be yourself. You’re totally unique. It’s just…ugh, I don’t know. I have to get to breakfast, Jake’ll be worried. I promise we’ll talk later.”

Finn broke his gaze as fast as possible to avoid that floored expression.


	2. Chapter 2

**Notes for the Chapter:**

> Musical inspiration: "Blind and Frozen" by Beast in Black

Fern’s mind reeled, as he sat dazed among the grass blades atop the tree house.

How he wished he could just fuse with the foliage, never to be seen again. Why did he even exist anyway? He’d gone from existing as a barely animate object to a donked up mess of plant and memories he wanted nothing to do with. Seriously, most of Finn’s existence had been a train wreck…and now the only one who understood the past Fern shared had just ditched him.

Sure, if Fern were honest, he wasn’t entirely sure what had just happened between them either - besides it being the best damn feeling from both Finn’s memories and his own as Fern. Not that he hadn’t enjoyable memories of making out with princesses, exploring on his own…Finn’s memories pre-Fern really couldn’t compare to their ride this morning.

So, why was Finn being so weird? Whatever, may as well act as though nothing was amiss…

 _He still thinks you’re him, that’s the problem_ , whispered that ever-present voice in his head.

 _I’m **not** him_… Fern thought, pursing his lips and resisting the urge to ball his hands into fists. _It’s just these stupid memories…the Grass Sword had nothing to do with Finn, he just bought it…_

 _You’re nothing without Finn, and he realizes that,_ that voice continued. _You’re nothing without me. You need us both. Use him and stick with me._

As ever, that wave of pure anguish overwhelmed his senses, consuming his every thought. The agony that swept through him at that voice, urging him against these feelings for the human who once wielded him, stung like a palpable thorn. Fern wracked a hand through his hair, pulling at the roots, to quell the voice in his head.

***

“What’s got your head all messed up?”

Jake’s question hung in the air over the breakfast table for close to a minute before registering with Finn.

“I…” Finn chose his words carefully, settling on half truth. “It’s Fern, I guess.”

“I thought that whole thing wasn’t bothering you,” Jake said, piling the last of the bacon onto a plate between them. “Wasn’t that where you were last night?”  
A cold sweat broke out on Finn’s nape. Thank Glob he’d managed to change out of his nightclothes and get downstairs before rousing his brother’s suspicions. “…Just figuring out some stuff.”

The more they talked about this, the more he felt like this might be the first topic his brother couldn’t help him with. As much as Finn hated to admit, he was finding he wanted to talk to someone more…human.

“Listen,” Jake’s voice brought Finn to attention once more, “you know I trust your judgment. I see what you mean now, about the guy not being harmful or anythin’…but he ain’t our brother, and I guess that’s why I was skeptical at first. I trust you though, man. Wherever you wanna take things as far as him staying here and stuff.”

Finn nodded, swallowing that annoying lump that burned his throat. Time to head to the swamp.

“Hey you, what’s going on?” Marceline’s smile and the humid scent of the river calmed his senses at least a tick. “Not that I mind a drop in…”

“Yeah, sorry about that,” Finn rubbed the back of his neck. “I didn’t really know where else to go…”“You need help?” Marcy asked, moving aside so he could enter the cabin. “Or just an ear?”

“Mostly an ear,” Finn replied, sitting on the couch. “It’s…well, don’t take this the wrong way but we’ve been friends a while, and…since Susan left, you’re the closest to human I could think of, and…wow, sorry, this is coming out all wrong….”

“This about Fern?”

“Oh…well, I…” Finn stammered.

“Phew, at least it’s not some weird love confession to me,” Marcy joked, and Finn allowed the slightest smile. 

“Did the “human” part clue you in?”

“Honestly,” said Marcy, “more the way you two act around each other. Like when he came to see you off on the beach when you and Jake went to the Islands? That was some crazy tension.”

“Yeah?” Finn couldn’t think of a more articulate response at the moment. 

“Dude, he literally inserted himself between you and Bonnie,” Marcy’s dark eyes glittered with mirth. “And by the way…the human part wouldn’t have spilt the beans. The guy’s not human…”

“I mean, I guess…” Glob, Finn wasn’t killin’ it with words today. Oh well, it was just Marcy. After briefly considering and deciding against bringing up what had happened with Fern at Bonnie’s lab, Finn decided to just keep his mouth shut and relish the silence.

“So, are you into him?” Marcy’s smile only grew wider.

“I…he’s like a clone, though…wouldn’t that be…”

“Not a clone, buddy. He’s an elemental, closer to something like Bonnie or FP. It’s a weird existence for sure. But I’m not hearing a “no”. So if it’s labels you’re worried about…I’d say you’ve fallen for your sword and leave it at that.”

“But, like…we share memories.”

“That makes the attraction even more inevitable,” Marcy said. “Think of all you guys share on top of all the new experiences you’ve had as separate people since. But whatever you do, try to remember he’s feeling mixed up about this whole thing too. Probably even more than you are.”

Finn just nodded.

“It’s the closest form of brotherhood and camaraderie, if you ask me,” Marcy went on. “You don’t always have to take responsibility for how you feel. Sometimes it’s healthiest to just embrace it instead of worrying that your feelings could mess up a situation. You and Bonnie could both do with a little less spazz in the overthinking department. But anyway, I know that hero look is still your jam. How many heroes have the opportunity to have a relationship with their sword?”

“He’s so much more than a sword,” Finn marveled at his first complete sentence since arriving here. “He can make himself look like me, but he’s not me and he’s not just a weapon. Not anymore. He...technically understands me more than anyone else ever has...more than anyone ever _could_ , I guess.”

“Exactly,” Marcy grinned. “You two get each other on a whole other level. In a thousand years, I've never seen anything quite like it. Now go talk to him.”

**Notes for the Chapter:**

> ...also a headcanon for why Finn evidently ends up single at the end of it all.

**Author's Note:**

> Headcanon on why Fern had the 180 from wanting to be his own person to suddenly wanting to take Finn's place.


End file.
